In the prior art, thermally expandable sheets in which a thermally expansive layer containing a thermally expandable material foaming and expanding according to the amount of heat absorbed is formed on one side of a base sheet are known. The thermally expansive layer can be distended in part or in whole by forming a photothermal conversion layer converting light to heat on the thermally expandable sheet and eradiating the photothermal conversion layer with light. Moreover, methods of forming a shaped object (stereoscopic image) on the thermally expandable sheet by changing the shape of the photothermal conversion layer are also known (for example, see Patent Literature Unexamined Japanese Patent Application Kokai Publication Nos. S64-28660 and 2001-150812).
In thermally expandable sheets, when heat is applied to thermally expansive layer, the thermally expansive layer is distensible in the direction opposite to surface on which the based is provided. In some cases, at this point, the underside of the thermally expansive layer peels-off from the base. Peel-off occurring between the base and the thermally expansive layer is problematic in that the peeled-off portion the thermally expansive layer cannot maintain the shape and height thereof and thus, when force is exerted, the shape and so on deforms.
Therefore, there is a demand for a thermally expandable sheet that can suppress peel-off of the thermally expansive layer from the base when the thermally expansive layer is distended.
The present disclosure is made with the view of the above situation and an objective of the disclosure is to provide a thermally expandable sheet that can suppress peel-off of the thermally expansive layer from the base when the thermally expansive layer is distended and a method of producing the thermally expandable sheet.